Reflective surfaces for ppg signal detection

ABSTRACT

Reflective surfaces for the apertures of PPG optical components in PPG systems is disclosed. In a PPG system or device, the addition of reflective surfaces around, under, or near the apertures of the optical components can enhance the amount of light received by the light detector. As a result, the measured PPG signal strength can be higher and more accurate compared to the same PPG device without reflective surfaces. The reflective surfaces can reflect and/or recycle light that is incident upon the reflective surfaces back into the skin for eventual capture of the light by the light detectors. In some examples, the reflective surfaces can be diffuse or specular reflectors and/or can be configured to selectively reflect one or more wavelengths of light. In some examples, the back crystal and/or component mounting plane of the PPG system can be made of the same material as the reflective surfaces.

CROSS REFERENCES TO RELATED APPLICATIONS

This is a continuation of U.S. patent application Ser. No. 14/470,834,filed Aug. 27, 2014 and published as U.S. Patent Publication No.2016-0058309 on Mar. 3, 2016; the contents of which are hereinincorporated by reference in its entirety for all intended purposes.

FIELD

This relates generally to a device that measures a photoplethysmographic(PPG) signal, and, more particularly, to reflective surfaces for PPGsignal detection.

BACKGROUND

A photoplethysmographic (PPG) signal can be measured by PPG systems toderive corresponding physiological signals (e.g., pulse rate). In abasic form, PPG systems can employ a light source or light emitter thatinjects light into the user's tissue, and a light detector to receivelight that reflects and/or scatters and exits the tissue. The receivedlight includes light with amplitude that is modulated as a result ofpulsatile blood flow (i.e., “signal”) and parasitic, non-signal lightwith amplitude that can be modulated (i.e., “noise” or “artifacts”)and/or unmodulated (i.e., DC). However, in some examples, the reflectedand/or scattered light received by the light detector may be have a lowsignal strength, making it difficult to accurately determine the user'spulse rate.

One way to increase the signal intensity or signal strength can be todecrease the distance between the light sensor and light emitter. Theminimum distance between the light sensor and light emitter can,however, be limited by mechanical or functional requirements of othercomponents on the PPG system, such as the windows used to cover andprotect the light source and light detector. An alternative way toincrease the signal strength may be needed.

SUMMARY

This relates to reflective surfaces around the apertures of PPG opticalcomponents in PPG systems. In a PPG system or device, the addition ofreflective surfaces around, under, or near the apertures of the opticalcomponents can enhance the amount of light received by the lightdetector. As a result, the measured PPG signal strength can be higherand more accurate compared to the same PPG device without reflectivesurfaces. The reflective surfaces can reflect and/or recycle light thatis incident upon the reflective surfaces back into the skin for eventualcapture of the light by the light detectors.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1C illustrate systems in which examples of the disclosure canbe implemented.

FIG. 2 illustrates an exemplary PPG signal according to examples of thedisclosure.

FIG. 3A illustrates a top view of an exemplary electronic deviceconfigured to measure a PPG signal according to examples of thedisclosure.

FIG. 3B illustrates a cross-sectional view of an exemplary electronicdevice configured to measure a PPG signal according to examples of thedisclosure.

FIG. 4A illustrates a top view of an exemplary electronic device withledges configured to measure a PPG signal according to examples of thedisclosure.

FIG. 4B illustrates a cross-sectional view of an exemplary electronicdevice with ledges configured to measure a PPG signal according toexamples of the disclosure.

FIGS. 4C-4F illustrate bar charts of measured modulated light,unmodulated light, perfusion index and signal-to-noise ratio of anexemplary device without ledges and an exemplary device with ledgesaccording to examples of the disclosure.

FIG. 5A illustrates a top view of an exemplary electronic device withincreased aperture sizes configured to measure a PPG signal according toexamples of the disclosure.

FIG. 5B illustrates a cross-sectional view of an exemplary electronicdevice with increased aperture sizes configured to measure a PPG signalaccording to examples of the disclosure.

FIGS. 5C-5F illustrate bar charts of measured modulated light values,unmodulated light values, perfusion index and signal-to-noise ratiovalues for an exemplary device without ledges, an exemplary device withledges, and an exemplary device with increased aperture sizes accordingto examples of the disclosure.

FIGS. 6A-6B illustrate top views of exemplary electronic devices withdifferent aperture sizes configured to measure a PPG signal according toexamples of the disclosure.

FIGS. 6C-6F illustrate bar charts of measured modulated light values,unmodulated light values, perfusion index and signal-to-noise ratiovalues for exemplary devices with different aperture sizes according toexamples of the disclosure.

FIG. 7A illustrates a top view of an exemplary electronic device withreflective surfaces configured to measure a PPG signal according toexamples of the disclosure.

FIGS. 7B-7E illustrate cross-sectional views of exemplary electronicdevices with reflective surfaces configured to measure a PPG signalaccording to examples of the disclosure.

FIG. 8 illustrates a block diagram of an exemplary computing systemcomprising light emitters and light sensors for measuring a PPG signalaccording to examples of the disclosure.

FIG. 9 illustrates an exemplary configuration in which a device isconnected to a host according to examples of the disclosure.

DETAILED DESCRIPTION

In the following description of examples, reference is made to theaccompanying drawings in which it is shown by way of illustrationspecific examples that can be practiced. It is to be understood thatother examples can be used and structural changes can be made withoutdeparting from the scope of the various examples.

In the following description, numerous specific details are set forth inorder to provide a thorough understanding of one or more aspects and/orfeatures described or referenced herein. It will be apparent, however,to one skilled in the art, that one or more aspects and/or featuresdescribed or referenced herein may be practiced without some or all ofthese specific details.

A photoplethysmographic (PPG) signal can be measured by PPG systems toderive corresponding physiological signals (e.g., pulse rate). Such PPGsystems can be designed to be sensitive to changes in blood in a user'stissue that can result from fluctuations in the amount or volume ofblood or blood oxygen in the vasculature of the user. In a basic form,PPG systems can employ a light source or light emitter that injectslight into the user's tissue, and a light detector to receive light thatreflects and/or scatters and exits the tissue. The PPG signal is theamplitude of reflected and/or scattered light that is modulated withvolumetric change in blood volume in the tissue. However, in someexamples, some of the reflected and/or scattered light can be lost,leading to a PPG signal measured by the light detector having a lowsignal strength. As a result, it may be difficult to accuratelydetermine the user's physiological state.

This disclosure relates to reflective surfaces around, under, on or nearone or more apertures of the PPG optical components. In a PPG device,the addition of reflective surfaces around, under, on or near theapertures of the optical components can enhance signal strength comparedto the same PPG device without reflective surfaces. The reflectivesurfaces can reflect or recycle light that is incident upon thereflective surfaces back into the skin for eventual capture of the lightby the light detectors. This incident light may not have been aseffectively reflected (if at all) without the reflective surfaces, andcould therefore be lost (i.e., not contribute to the signal measured bythe light detector).

Representative applications of methods and apparatus according to thepresent disclosure are described in this section. These examples arebeing provided solely to add context and aid in the understanding of thedescribed examples. It will thus be apparent to one skilled in the artthat the described examples may be practiced without some or all of thespecific details. Other applications are possible, such that thefollowing examples should not be taken as limiting.

FIGS. 1A-1C illustrate systems in which examples of the disclosure canbe implemented. FIG. 1A illustrates an exemplary mobile telephone 136that can include a touch screen 124. FIG. 1B illustrates an exemplarymedia player 140 that can include a touch screen 126. FIG. 1Cillustrates an exemplary wearable device 144 that can include a touchscreen 128 and can be attached to a user using a strap 146. The systemsof FIGS. 1A-1C can utilize the reflective surfaces as will be disclosed.

FIG. 2 illustrates an exemplary PPG signal absent of artifacts. Signal210 can be light measured by one or more light detectors and processedsuch that artifacts are optionally removed or extracted from the signal.Signal 210 can include light information with an amplitude that ismodulated as a result of pulsatile blood flow (i.e., “signal”) andparasitic, unmodulated, non-signal light (i.e., DC). From the measuredPPG signal 210, a perfusion index can be determined. The perfusion indexcan be the ratio of received modulated light (ML) to unmodulated light(UML) (i.e., ratio of blood flow modulated signal to static, parasiticDC signal) and can give extra information regarding the user'sphysiological state. The modulated light (ML) can be the peak-to-valleyvalue of signal 210, and unmodulated light (UML) can be thezero-to-average (using average 212) value of signal 210. As shown inFIG. 2, the perfusion index can be equal to the ratio of ML to UML.

FIG. 3A illustrates a top view, and FIG. 3B illustrates across-sectional view of an exemplary electronic device configured tomeasure a PPG signal. Device 300 can include light emitters 306 and 316and light sensors 304 and 314 located on a surface of device 300. Lightemitters 306 and 316 and light sensors 304 and 314 can be facing towardsa skin 320 of a user. Between light emitter 306 (or any one or more oflight emitter 316 and light sensors 304 and 314) and skin 320 can bewindows 301 surrounded by back crystal 318. Windows 301 can have adiameter 312 and can be mounted to device 300 using an adhesive 322 onthe sides of windows 301. Device 300 can optionally include opticalisolation 319. Light emitters 306 and 316 can be any type of lightsource, including but not limited to, light emitting diodes (LEDs),incandescent lights, fluorescent lights, organic light emitting diodes(OLEDs), and electroluminescent diodes (ELDs). Light sensors 304 and 314can be any type of optical sensing device such as a photodiode. In someexamples, light emitters 306 and 316 and/or light sensors 304 and 314can be mounted or touching a component mounting plane 346. In someexamples, either light sensors 304 and 314 or light emitters 306 and 314or both can be symmetrically placed with respect to the center of theback crystal 318. In some examples, either light sensors 304 and 314 orlight emitters 306 and 316 or both can be asymmetrically placed withrespect to the center of the back crystal 318.

In some examples, adhesive 322 applied to the sides of the windows 301can be insufficient for effectively attaching windows 301 to device 300.For such a case, back crystal 318 can be designed to improve mechanicalstability. FIG. 4A illustrates a top view, and FIG. 4B illustrates across-sectional view of an exemplary electronic device configured tomeasure a PPG signal according to examples of the disclosure. Device 400can include light emitters 406 and light sensors 404 located on asurface of device 400. Light emitters 406 and light sensors 404 can befacing towards a skin 420 of a user and can be mounted to or touching acomponent mounting plane 446. In some examples, light emitters 406 canbe y-centered (i.e., symmetrically placed along the horizontal axis).Between light emitters 406 (or light sensors 404) and skin 420 can bewindows 401 surrounded by back crystal 418. Back crystal 418 can includeledges 448 for improving the mechanical stability of device 400 byproviding a larger surface area for windows 401 to rest on and/or adhereto. Windows 401 can have a diameter 412 and can be mounted to device 400using an adhesive 422 to attach the sides of windows 401 and at least aportion of one side of windows 401 to ledges 448. While back crystal 418can improve the adhesion of windows 401 to back crystal 418, the ledges448 may lead to a smaller aperture or diameter 413 than for deviceswithout a ledge (such as illustrated in FIGS. 3A-3B). Device 400 canoptionally include optical isolation 419.

The smaller diameter 413 can lead to a lower amount of light reachingskin 420 from light emitters 406 and/or a lower amount of lightreflecting or scattering back and being sensed by light sensors 404. Asa result, the light intensity and measured signal strength may bereduced. FIG. 4C illustrates a bar chart of measured modulated light ofan exemplary device without ledges and an exemplary device with ledgesaccording to examples of the disclosure. A device with ledges (such asdevice 400 shown in FIGS. 4A-4B) can have a lower modulated light signalthan a device without ledges (such as device 300 shown in FIGS. 3A-3B).As discussed above, the lower modulated light signal can be due to achange in aperture size. For example, diameter 312 or 412 can be 6.1 mm,and diameter 413 can be 3.9 mm. In the present example, ledges 448 indevice 400 can lead to an optical aperture that can be reduced by 2.2 mmin diameter or 69.12 mm² in area. The device without ledges (device 300)can have a modulated light signal value of 392 pA/mA from the shorterpath (path 391) and a modulated light signal value of 309 pA/mA from thelonger path (path 393). The device with ledges (device 400) can have amodulated light signal value of 197 pA/mA, which is at least 50% lowerthan the modulated light signal values of the device without ledges(device 300).

In addition to a lower modulated light signal, ledges 448 in device 400can result in a lower unmodulated light signal as shown in FIG. 4D. Forexample, the device without ledges (device 300) can have an unmodulatedlight signal value of 22.2 nA/mA from path 391 and an unmodulated lightsignal value of 17.0 nA/mA from path 393. The device with ledges (device400) can have an unmodulated light signal value of 7.5 nA/mA, which isat least 55% lower than the unmodulated light signal values of thedevice without ledges (device 300).

As discussed above, the perfusion index is equal to the ratio ofmodulated light to unmodulated light. FIG. 4E illustrates a bar chart ofthe perfusion index of an exemplary device without ledges and anexemplary device with ledges according to examples of the disclosure.Although the device without ledges (device 300) can have a highermodulated light signal and a higher unmodulated light signal than adevice with ledges (device 400), the perfusion index can be lower. Forexample, the device without ledges (device 300) can have a perfusionindex from the shorter path (path 391) of 1.7% and a perfusion indexfrom the longer path (path 393) of 1.73%, whereas the device with ledges(device 400) can have a perfusion index of 2.36%.

Additionally, the device with ledges (device 400) can have a lowersignal-to-noise ratio than the device without ledges (device 300), asillustrated in FIG. 4F. For example, the shorter path (path 391) of thedevice without ledges (device 300) can have a signal-to-noise ratio of9.6 bits, and the longer path (path 393) of the device without ledges(device) 300 can have a signal-to-noise ratio of 9.3 bits. The devicewith ledges (device 400) can have a lower signal-to-noise ratio value of8.3 bits.

As illustrated in FIGS. 4C-4F, the device with ledges can lead to areduced signal intensity. However, removing the ledges or manufacturinga device without ledges can result in a device with poor mechanicalstability to secure or attach the windows. A different method toincreasing the signal intensity may be needed. FIG. 5A illustrates a topview, and FIG. 5B illustrates a cross-sectional view of an exemplaryelectronic device configured to measure a PPG signal according toexamples of the disclosure. Device 500 can include light emitters 506and light sensors 504 attached to or touching component mounting plane546. Device 500 can optionally include optical isolation 519. Windows501 with a diameter 512 can be included for covering and/or protectinglight emitters 506 and light sensors 504. Back crystal 518 can bedisposed around windows 501. Windows 501 can be touching or attached(using adhesive 522) to ledges 548. Light can be emitted from lightemitters 506 towards a skin 520 of a user. Light can reflect and/orscatter off skin 520, vasculature, and blood of the user and reflectback towards light sensor 504. To increase the signal intensity, adiameter 515 of the apertures can be made larger than diameter 413 ofFIGS. 4A-4B.

FIGS. 5C-5F illustrate bar charts of measured modulated light values,unmodulated light values, perfusion index, and signal-to-noise ratiovalues for an exemplary device without ledges (device 300 of FIGS.3A-3B), an exemplary device with ledges (device 400 of FIGS. 4A-4B), andan exemplary device with increased aperture size (device 500 of FIGS.5A-5B) according to examples of the disclosure. For example, a diameter515 of the device with increase aperture size (device 500) can be 4.9mm, whereas a diameter 413 of the device with ledges (device 400) can be3.9 mm. In some examples, the device with increased aperture size(device 500) can include ledges. The increased aperture size (device500) can lead to an increase in measured modulated light values. Asshown in FIG. 5C, the device without ledges (device 300) can have amodulated light signal value of 257 pA/mA from the shorter path (path391) and a modulated light signal value of 181 pA/mA from longer path(path 393). The addition of ledges 448 (device 400) can lead to a lowermodulated light signal value of 94 pA/mA. However, the reduced intensitycan be compensated by increasing the aperture size (device 500). Thedevice with increased aperture size (device 500) can have a modulatedlight signal value of 262 pA/mA, which is comparable to device 300 (thedevice without ledges). As shown in FIG. 5D, increasing the aperturesize can also result in measured unmodulated light values for the devicewith increased aperture size (device 500) higher than measuredunmodulated light values for the device without ledges (device 300). Forexample, the unmodulated light values for the device without ledges(device 300) can be 23.6 nA/mA for the shorter path (path 391) or 16.2nA/mA for the longer path (path 393), 7.9 nA/mA for the device withledges (device 400), and 29.7 nA/mA for the device with increaseaperture size (device 500). Although increasing the aperture size canlead to a higher signal strength for measured modulated light, themeasured unmodulated light (or noise) can increase as well.

FIG. 5E illustrates an exemplary bar chart for perfusion index. Thedevice without ledges (device 300) can have a perfusion index of1.16-1.17%, the device with ledges (device 400) can have a perfusionindex of 1.29%, and the device with increased aperture size (device 500)can have a perfusion index of 1.01%. Although the signal strength formodulated light increases, the perfusion index can be lower for thedevice with increase aperture size (device 500) due to the measuredunmodulated light value also increasing. FIG. 5F illustrates comparablesignal-to-noise ratio values for the device without ledges (device 300)and the device with ledges (device 500). The device without ledges(device 300) can have a signal-to-noise ratio value of between 8.9-9.4bits. The device with ledges (device 400) can have a lowersignal-to-noise ratio of 7.9 bits, while the device with increasedaperture size (device 500) can have a signal-to-noise ratio of 9.2 bits.

FIGS. 6A-6B illustrate top views of exemplary electronic devices withdifferent aperture sizes configured to measure a PPG signal according toexamples of the disclosure. Device 600 of FIG. 6A can include lightsensors 604 and windows 601 covering and/or protecting light sensors604. Windows 601 can be attached to or touching ledges 646. Theapertures associated with light sensors 604 and windows 601 can have adiameter 613. Device 600 can also include light emitters 606 and windows603 covering and/or protecting light emitters 606. Windows 603 can beattached to or touching ledges 648. The apertures associated with lightemitters 606 and windows 603 can have a diameter 615. In some examples,diameter 613 can be smaller than diameter 615 due to a size differencebetween ledges 646 and 648. That is, light sensors 604 can receive lightthrough smaller sized apertures than light emitters 606 emit light.

Device 650 of FIG. 6B can include light sensors 654 and windows 653covering and/or protecting light sensors 654. Windows 653 can beattached to or touching ledges 698. The apertures associated with lightsensors 654 and windows 653 can have a diameter 665. Device 650 can alsoinclude light emitters 656 and windows 651 covering and/or protectinglight emitters 656. Windows 651 can be attached to or touching ledges696. The apertures associated with light emitters 656 and windows 651can have a diameter 663. In some examples, diameter 663 can be smallerthan diameter 665 due to a size difference between ledges 696 and 698.That is, light sensors 654 can receive light through larger sizedapertures than light emitters 656 can emit light.

FIGS. 6C-6F illustrate bar charts of measured modulated light values,unmodulated light values, perfusion index and signal-to-noise ratiovalues for exemplary devices with different aperture sizes according toexamples of the disclosure. For example, diameters 613 and 663 can be3.9 mm, diameters 615 and 665 can be 4.9 mm, and diameters 612 and 662of windows 612 can be 6.12 mm. As shown in FIG. 6C, the modulated lightvalue is comparable for device 600 and 650. That is, selectivelychoosing which one of the light emitters 606 and 656 or light sensors604 and 654 is associated with the larger sized aperture may not have asignificant effect on the modulated light value. Similarly, as shown inFIG. 6D, the unmodulated light value is comparable for the device withlarger aperture size associated with the light emitters (device 600) andfor the device with larger aperture size associated with the lightsensors (device 650). FIG. 6E shows comparable perfusion indices for thedevice with larger aperture size associated with the light emitters(device 600) and the device with larger aperture size associated withthe light sensors (device 650), and FIG. 6F shows comparablesignal-to-noise ratio values. The highest modulated light value andunmodulated light value can be achieved with device 500 (i.e., thedevice with largest aperture sizes for both light emitters and lightsensors). However, device 500 can also have the lowest perfusion indexand highest signal-to-noise ratio.

While increasing the aperture size may effectively increase themodulated signal strength and the unmodulated signal strength, theperfusion decreases and the signal-to-noise ratio increases. Analternative solution to increasing the signal intensity may be desired.FIG. 7A illustrates a top view, and FIG. 7B illustrates across-sectional view of an exemplary electronic device with reflectivesurfaces configured to measure a PPG signal according to examples of thedisclosure. Device 700 can include one or more light emitters 706, oneor more light sensors 704, and a plurality of windows 701 protectingand/or covering the light emitters 706 and light sensors 704. The lightemitters 706 and light sensors 704 can be mounted on or touching acomponent mounting plane 746, and windows 701 can be mounted, adheredto, or touching a back crystal 718. Back crystal 718 can include ledges748 for attaching windows 701 using adhesive 722. Light emitted fromlight emitters 706 can be directed towards a skin 720 of a user topenetrate through the skin 720, vasculature, and/or blood and reflectand/or scatter back to device 700 to be sensed by light sensors 704. Insome examples, the light reflected back can be lost and absorbed by backcrystal 718. As a result, the signal strength of the light sensed bylight sensors 704 may be reduced in intensity.

One way to minimize the loss of reflected light can be to utilizereflective surfaces as illustrated in FIGS. 7B-7E. Device 700 can beformed by at least forming component mounting plane 746, attaching lightemitters 706 and light sensors 704 to component mounting plane 746, andforming back crystal 718 and ledges 748. Device 700 can optionallyinclude optical isolation 719. As illustrated in FIG. 7B, reflectivesurfaces 747 can be disposed on one or more sides of ledges 748 facingskin 720. Reflective surfaces 747 can be disposed using any number ofdeposition techniques including chemical vapor deposition, physicalvapor deposition, plating, printing, or spray processes. In someexamples, reflective surfaces 747 can be formed separately and can beattached to or touching ledges 748. With reflective surfaces 747,reflected light incident on ledges 748 can be reflected and/or scatteredback to skin 720 and can be recycled instead of being lost. Reflectivesurfaces 747 can be made of any type of reflective material including,but not limited to, white ink, silver ink, and silver foil. In someexamples, adhesive 722 can be made of a transparent material.

In some examples, reflective surfaces 747 can be disposed on or attachedto adhesive 722, where adhesive 722 can be applied to ledges 748, asillustrated in FIG. 7C. Adhesive 722 can be a transparent material orcan be an opaque material. In some examples, reflective surfaces 747 canbe located between adhesive 722 and windows 701, but disposed on windows701 instead of being disposed on adhesive 722. In some examples,reflective surfaces 747 can be disposed on windows 701 between windows701 and skin 720. That is, neither adhesive 722 nor windows 701 arebetween reflective surfaces 747 and skin 720, as illustrated in FIG. 7D.In some examples, reflective surfaces 747 can be disposed on the innersides of back crystal 718 cavity or orthogonal to a surface of skin 720,as illustrated in FIG. 7E. With reflective surfaces 747 disposed on theinner sides of back crystal 718 cavity, reflected light incident on theinner sides can reflect and/or scatter back towards skin 720 and can berecycled to minimize any lost or absorbed light signal.

In some examples, the reflective surfaces 747 can be specularreflectors. Light with a single incoming direction can be reflected witha single outgoing direction (as shown in FIGS. 7B and 7E). An exemplaryspecular reflector can be silver foil. In some examples, the reflectivesurfaces 747 can be diffuse reflectors. Light with a single incomingdirection can be reflected in a broad range of directions. An exemplarydiffuse reflector can be white ink. In some examples, reflectivesurfaces 747 can be a combination of a specular reflector and a diffusereflector. In some examples, one or more reflective surfaces 747 can bespecular reflectors, while the other reflective surfaces 747 can bediffuse reflectors.

In some examples, reflective surfaces 747 can selectively reflect and/orscatter one or more colors, while absorbing all other colors. Forexample, reflective surfaces 747 can be configured to reflect and/orscatter green light, while absorbing all other colors and wavelengths oflight. To selectively reflect and/or scatter green light, reflectivesurfaces 747 can be made of a green-colored coating or foil, forexample.

In some examples, reflective surfaces 747 can be made of a pattern orgrating to control the optical paths or light angles or preferentiallydirect the light to travel along specific paths. In some examples,reflective surfaces 747 can be configured to reflect and/or scatter onewavelength of light in one direction and reflect and/or scatter anotherwavelength of light in another direction. For example, red light canenter the skin 720 of a user with shallow angles. As a result, red lightmay not penetrate deep enough to reach pulsatile blood. Reflectivesurfaces 747 can be configured to direct red light with an angle suchthat the red light is head-on or near head-on with skin 720 instead ofat a glancing angle.

In some examples, one or more of back crystal 718 and component mountingplane 746 can be made of a reflective material. In some examples, backcrystal 718 and component mounting plane 746 can be made of the samematerial. In some examples, back crystal 718 or component mounting plane746 or both can be the same material as reflective surfaces 747. In someexamples, adhesive 722 can be made of a reflective material.

FIG. 8 illustrates an exemplary block diagram of a computing systemcomprising light emitters and light sensors for measuring a PPG signalaccording to examples of the disclosure. Computing system 800 cancorrespond to any of the computing devices illustrated in FIGS. 1A-1C.Computing system 800 can include a processor 810 configured to executeinstructions and to carry out operations associated with computingsystem 800. For example, using instructions retrieved from memory,processor 810 can control the reception and manipulation of input andoutput data between components of computing system 800. Processor 810can be a single-chip processor or can be implemented with multiplecomponents.

In some examples, processor 810 together with an operating system canoperate to execute computer code and produce and use data. The computercode and data can reside within a program storage block 802 that can beoperatively coupled to processor 810. Program storage block 802 cangenerally provide a place to hold data that is being used by computingsystem 800. Program storage block 802 can be any non-transitorycomputer-readable storage medium, and can store, for example, historyand/or pattern data relating to PPG signal and perfusion index valuesmeasured by one or more light sensors such as light sensors 804. By wayof example, program storage block 802 can include Read-Only Memory (ROM)818, Random-Access Memory (RAM) 822, hard disk drive 808 and/or thelike. The computer code and data could also reside on a removablestorage medium and loaded or installed onto the computing system 800when needed. Removable storage mediums include, for example, CD-ROM,DVD-ROM, Universal Serial Bus (USB), Secure Digital (SD), Compact Flash(CF), Memory Stick, Multi-Media Card (MMC) and a network component.

Computing system 800 can also include an input/output (I/O) controller812 that can be operatively coupled to processor 810, or it can be aseparate component as shown. I/O controller 812 can be configured tocontrol interactions with one or more I/O devices. I/O controller 812can operate by exchanging data between processor 810 and the I/O devicesthat desire to communicate with processor 810. The I/O devices and I/Ocontroller 812 can communicate through a data link. The data link can bea one-way link or a two-way link. In some cases, I/O devices can beconnected to I/O controller 812 through wireless connections. By way ofexample, a data link can correspond to PS/2, USB, Firewire, IR, RF,Bluetooth or the like.

Computing system 800 can include a display device 824 that can beoperatively coupled to processor 810. Display device 824 can be aseparate component (peripheral device) or can be integrated withprocessor 810 and program storage block 802 to form a desktop computer(e.g., all-in-one machine), a laptop, handheld or tablet computingdevice of the like. Display device 824 can be configured to display agraphical user interface (GUI) including perhaps a pointer or cursor aswell as other information to the user. By way of example, display device824 can be any type of display including a liquid crystal display (LCD),an electroluminescent display (ELD), a field emission display (FED), alight emitting diode display (LED), an organic light emitting diodedisplay (OLED) or the like.

Display device 824 can be coupled to display controller 826 that can becoupled to processor 810. Processor 810 can send raw data to displaycontroller 826, and display controller 826 can send signals to displaydevice 824. Data can include voltage levels for a plurality of pixels indisplay device 824 to project an image. In some examples, processor 810can be configured to process the raw data.

Computing system 800 can also include a touch screen 830 that can beoperatively coupled to processor 810. Touch screen 830 can be acombination of sensing device 832 and display device 824, where thesensing device 832 can be a transparent panel that is positioned infront of display device 824 or integrated with display device 824. Insome cases, touch screen 830 can recognize touches and the position andmagnitude of touches on its surface. Touch screen 830 can report thetouches to processor 810, and processor 810 can interpret the touches inaccordance with its programming. For example, processor 810 can performtap and event gesture parsing and can initiate a wake of the device orpowering on one or more components in accordance with a particulartouch.

Touch screen 830 can be coupled to a touch controller 840 that canacquire data from touch screen 830 and can supply the acquired data toprocessor 810. In some cases, touch controller 840 can be configured tosend raw data to processor 810, and processor 810 can process the rawdata. For example, processor 810 can receive data from touch controller840 and can determine how to interpret the data. The data can includethe coordinates of a touch as well as pressure exerted. In someexamples, touch controller 840 can be configured to process raw dataitself. That is, touch controller 840 can read signals from sensingpoints 834 located on sensing device 832 and can turn the signals intodata that the processor 810 can understand.

Touch controller 840 can include one or more microcontrollers such asmicrocontroller 842, each of which can monitor one or more sensingpoints 834. Microcontroller 842 can, for example, correspond to anapplication specific integrated circuit (ASIC), which works withfirmware to monitor the signals from sensing device 832, process themonitored signals, and report this information to processor 810.

One or both display controller 826 and touch controller 840 can performfiltering and/or conversion processes. Filtering processes can beimplemented to reduce a busy data stream to prevent processor 810 frombeing overloaded with redundant or non-essential data. The conversionprocesses can be implemented to adjust the raw data before sending orreporting them to processor 810.

In some examples, sensing device 832 can be based on capacitance. Whentwo electrically conductive members come close to one another withoutactually touching, their electric fields can interact to form acapacitance. The first electrically conductive member can be one or moreof the sensing points 834, and the second electrically conductive membercan be an object 890 such as a finger. As object 890 approaches thesurface of touch screen 830, a capacitance can form between object 890and one or more sensing points 834 in close proximity to object 890. Bydetecting changes in capacitance at each of the sensing points 834 andnoting the position of sensing points 834, touch controller 840 canrecognize multiple objects, and determine the location, pressure,direction, speed and acceleration of object 890 as it moves across thetouch screen 830. For example, touch controller 890 can determinewhether the sensed touch is a finger, tap, or an object covering thesurface.

Sensing device 832 can be based on self-capacitance or mutualcapacitance. In self-capacitance, each of the sensing points 834 can beprovided by an individually charged electrode. As object 890 approachesthe surface of the touch screen 830, the object can capacitively coupleto those electrodes in close proximity to object 890, thereby stealingcharge away from the electrodes. The amount of charge in each of theelectrodes can be measured by the touch controller 840 to determine theposition of one or more objects when they touch or hover over the touchscreen 830. In mutual capacitance, sensing device 832 can include a twolayer grid of spatially separated lines or wires (not shown), althoughother configurations are possible. The upper layer can include lines inrows, while the lower layer can include lines in columns (e.g.,orthogonal). Sensing points 834 can be provided at the intersections ofthe rows and columns. During operation, the rows can be charged, and thecharge can capacitively couple from the rows to the columns. As object890 approaches the surface of the touch screen 830, object 890 cancapacitively couple to the rows in close proximity to object 890,thereby reducing the charge coupling between the rows and columns. Theamount of charge in each of the columns can be measured by touchcontroller 840 to determine the position of multiple objects when theytouch the touch screen 830.

Computing system 800 can also include one or more light emitters such aslight emitters 806 and one or more light sensors such as light sensors804 proximate to skin 820 of a user. Light emitters 806 can beconfigured to generate light, and light sensors 804 can be configured tomeasure a light reflected or absorbed by skin 820, vasculature, and/orblood of the user. Device 800 can include reflective surfaces 847coupled to light emitters 806 and light sensors 804. Reflective surfaces847 can be configured to reflected light incident on ledges or the backcrystal (not shown) towards skin 820 to be recycled instead of beinglost. Light sensor 804 can send measured raw data to processor 810, andprocessor 810 can perform noise and/or artifact cancellation todetermine the PPG signal and/or perfusion index. Processor 810 candynamically activate light emitters and/or light sensors based on anapplication, user skin type, and usage conditions. In some examples,some light emitters and/or light sensors can be activated, while otherlight emitters and/or light sensors can be deactivated to conservepower, for example. In some examples, processor 810 can store the rawdata and/or processed information in a ROM 818 or RAM 822 for historicaltracking or for future diagnostic purposes.

In some examples, the light sensors can measure light information and aprocessor can determine a PPG signal and/or perfusion index from thereflected or absorbed light. Processing of the light information can beperformed on the device as well. In some examples, processing of lightinformation need not be performed on the device itself. FIG. 9illustrates an exemplary configuration in which a device is connected toa host according to examples of the disclosure. Host 910 can be anydevice external to device 900 including, but not limited to, any of thesystems illustrated in FIGS. 1A-1C or a server. Device 900 can beconnected to host 910 through communications link 920. Communicationslink 920 can be any connection including, but not limited to, a wirelessconnection and a wired connection. Exemplary wireless connectionsinclude Wi-Fi, Bluetooth, Wireless Direct and Infrared. Exemplary wiredconnections include Universal Serial Bus (USB), FireWire, Thunderbolt,or any connection requiring a physical cable.

In operation, instead of processing light information from the lightsensors on the device 900 itself, device 900 can send raw data 930measured from the light sensors over communications link 920 to host910. Host 910 can receive raw data 930, and host 910 can process thelight information. Processing the light information can includecanceling or reducing any noise due to artifacts and determiningpsychological signals such as a user's heart rate. Host 910 can includealgorithms or calibration procedures to account for differences in auser's characteristics affecting PPG signal and perfusion index.Additionally, host 910 can include storage or memory for tracking a PPGsignal and perfusion index history for diagnostic purposes. Host 910 cansend the processed result 940 or related information back to device 900.Based on the processed result 940, device 900 can notify the user oradjust its operation accordingly. By offloading the processing and/orstorage of the light information, device 900 can conserve space andpower enabling device 900 to remain small and portable, as space thatcould otherwise be required for processing logic can be freed up on thedevice.

In some examples, an electronic device is disclosed. The electronicdevice may comprise: one or more light emitters configured to generateone or more light paths through one or more apertures; one or moresensors configured to detect a reflection of the one or more lightpaths; one or more reflective surfaces in contact with the one or moreapertures; and logic coupled to the one or more sensors and configuredto detect a signal from the one or more reflected light paths.Additionally or alternatively to one or more examples disclosed above,in other examples, at least one of the one or more reflective surfacesis a diffuse reflector. Additionally or alternatively to one or moreexamples disclosed above, in other examples, the diffuse reflector is awhite ink. Additionally or alternatively to one or more examplesdisclosed above, in other examples, at least one of the one or morereflective surfaces is a specular reflector. Additionally oralternatively to one or more examples disclosed above, in otherexamples, the specular reflector is a silver foil. Additionally oralternatively to one or more examples disclosed above, in otherexamples, at least one of the one or more reflective surfaces includes agrating or pattern. Additionally or alternatively to one or moreexamples disclosed above, in other examples, the grating or pattern isconfigured to change an angle of at least one of the one or morereflected light paths. Additionally or alternatively to one or moreexamples disclosed above, in other examples, at least one of the one ormore reflective surfaces is a combination of diffuse and specularreflectors. Additionally or alternatively to one or more examplesdisclosed above, in other examples, at least one of the one or morereflective surfaces is configured to selectively reflect one or morewavelengths. Additionally or alternatively to one or more examplesdisclosed above, in other examples, a color of the at least one of theone or more reflective surfaces is associated with the selectivelyreflected one or more wavelengths. Additionally or alternatively to oneor more examples disclosed above, in other examples, at least one of theone or more apertures is a different size than another of the one ormore apertures. Additionally or alternatively to one or more examplesdisclosed above, in other examples, the device further comprises: a backcrystal in contact with the one or more apertures; and a componentmounting plane configured for attaching to the one or more lightemitters and the one or more sensors, wherein at least one of the backcrystal and the component mounting plane is reflective. Additionally oralternatively to one or more examples disclosed above, in otherexamples, at least one of the back crystal and the component mountingplane is a same material as at least one of the one or more reflectivesurfaces. Additionally or alternatively to one or more examplesdisclosed above, in other examples, the device further comprises: one ormore windows configured to cover the one or more light emitters and theone or more sensors; and a reflective adhesive configured to attach theone or more windows to the electronic device. Additionally oralternatively to one or more examples disclosed above, in otherexamples, at least one of the one or more apertures has a diameterbetween 3.9 mm-4.9 mm.

In some examples, a method for determining a physiological signal froman electronic device is disclosed. The method may comprise: emittinglight through one or more apertures to generate one or more light paths;receiving light from a reflection of the one or more light paths off atleast one or more reflective surfaces in contact with the one or moreapertures; and determining the physiological signal from the receivedlight. Additionally or alternatively to one or more examples disclosedabove, in other examples, the electronic device further includes a backcrystal in contact with the one or more apertures, a component mountingplane in contact with the one or more light emitters and the one or moresensors, one or more windows, and an adhesive configured to attach theone or more windows to the electronic device, the method furthercomprising receiving light from a reflection off at least one of theback crystal, the component mounting plane, and the adhesive.Additionally or alternatively to one or more examples disclosed above,in other examples, the method further comprises changing an angle of atleast one of the one or more reflected light paths. Additionally oralternatively to one or more examples disclosed above, in otherexamples, the method further comprises selectively reflecting one ormore wavelengths of the light.

In some examples, a method of a first device communicating with a seconddevice is disclosed. The method may comprise: sending, to a seconddevice, a measured reflected signal from one or more reflective surfacesin contact with one or more apertures of the first device; andreceiving, from the second device, a physiological signal.

Although the disclosed examples have been fully described with referenceto the accompanying drawings, it is to be noted that various changes andmodifications will become apparent to those skilled in the art. Suchchanges and modifications are to be understood as being included withinthe scope of the disclosed examples as defined by the appended claims.

What is claimed is:
 1. An electronic device comprising: a plurality oflight emitters for emitting first light; a light emitting sectionincluding: a plurality of first cavities through which the first lightis emitted, and a plurality of first reflectors circumferentiallysurrounding the plurality of first cavities; a plurality of lightsensors for receiving second light; and a light sensing sectionincluding: a plurality of second cavities through which the second lightis received, and a plurality of second reflectors circumferentiallysurrounding the plurality of second cavities.
 2. The electronic deviceof claim 1, wherein the light emitting section further includes aplurality of first windows, and the light sensing section furtherincludes a plurality of second windows.
 3. The electronic device ofclaim 2, further comprising: an optical isolation located between theplurality of first cavities and the plurality of second cavities,wherein the plurality of first reflectors is located between the opticalisolation and the plurality of first windows, and wherein the pluralityof second reflectors is located between the optical isolation and theplurality of second windows.
 4. The electronic device of claim 2,further comprising: a back crystal, wherein first portions of the backcrystal form first ledges and second portions of the back crystal formsecond ledges, wherein the plurality of first windows is attached to ortouching the first ledges, and the plurality of second windows isattached to or touching the second ledges.
 5. The electronic device ofclaim 4, further comprising: an optical isolation located between theplurality of first cavities and the plurality of second cavities,wherein the first ledges are located between the optical isolation andthe plurality of first windows, and the second ledges are locatedbetween the optical isolation and the plurality of second windows. 6.The electronic device of claim 4, further comprising: adhesive locatedbetween the first ledges and the plurality of first windows and furtherlocated between the second ledges and the plurality of second windows.7. The electronic device of claim 2, wherein the plurality of lightemitters emits the first light through top and bottom surfaces of theplurality of first windows, wherein a portion of the plurality of firstreflectors is located along side surfaces of the plurality of firstwindows.
 8. The electronic device of claim 2, wherein the plurality oflight emitter emits the first light through top and bottom surfaces ofthe plurality of first windows, wherein at least a portion of theplurality of first reflectors is located along portions of the topsurface of the plurality of first windows.
 9. The electronic device ofclaim 2, wherein the plurality of light sensors receives the secondlight through top and bottom surfaces of the plurality of secondwindows, wherein a portion of the plurality of second reflectors islocated along side surfaces of the plurality of second windows.
 10. Theelectronic device of claim 2, wherein the plurality of light sensorsreceives the first light through top and bottom surfaces of theplurality of second windows, wherein at least a portion of the pluralityof second reflectors is located along portions of the top surface of theplurality of second windows.
 11. The electronic device of claim 2,wherein the plurality of first windows is located between the pluralityof first reflectors and the plurality of first cavities, and theplurality of second windows is located between the plurality of secondreflectors and the plurality of second cavities.
 12. The electronicdevice of claim 1, wherein the plurality of first cavities has firstapertures with first sizes, and the plurality of second cavities hassecond apertures with second sizes, the second sizes being less than thefirst sizes.
 13. The electronic device of claim 12, wherein the lightemitting section further includes a plurality of first windows, and thelight sensing section further includes a plurality of second windows,wherein diameters of the plurality of first windows are larger than thefirst sizes, and diameters of the plurality of second windows are largerthan the second sizes.
 14. The electronic device of claim 1, wherein theplurality of second reflectors is configured to selectively return oneor more colors of incident light while selectively absorbing one or moreother colors of the incident light.
 15. The electronic device of claim1, wherein the plurality of first reflectors, the plurality of secondreflectors, or both include a pattern or a grating for selectivelydirecting incident light based one or more properties of the incidentlight.
 16. The electronic device of claim 1, wherein the selectivedirection of the incident light includes: returning a portion of theincident light having a first wavelength in a first direction, andreturning a portion of the incident light having a second wavelength ina second direction, the first wavelength different from the secondwavelength, and the first direction different from the second direction.17. The electronic device of claim 1, wherein reflecting surfaces of theplurality of first reflectors face an external housing of the device,and reflecting surfaces of the plurality of first reflectors face theexternal housing of the device.
 18. A method for operating an opticalsensing system, the method comprising: emitting first light from aplurality of light emitters through a light emitting section, the lightemitting section including a plurality of first cavities, a plurality offirst reflectors, and a plurality of first windows, wherein theplurality of first reflectors circumferentially surrounds the pluralityof first cavities; returning at least a portion of the first light usingthe plurality of first reflectors; receiving second light by a pluralityof light sensors through a light receiving section, the light receivingsection including a plurality of second cavities, a plurality of secondreflectors, and a plurality of second windows, wherein the plurality ofsecond reflectors circumferentially surrounds the plurality of secondcavities; and returning at least a portion of light incident on theplurality of second reflectors.
 19. The method of claim 18, wherein theportion of light incident on the plurality of second reflectors to askin of a user.
 20. The method of claim 18, wherein at least a portionof the received second light includes the portion of the light incidenton the plurality of second reflectors.